This invention relates to molding compositions containing a vulcanizable elastomer and molded objects made therefrom, particularly to molded containers having the look and feel of clay or terra cotta. More particularly, this invention relates to horticultural containers such as flowerpots and saucers as well as to containers useful for cooling beverage bottles such as wine bottles, and other molded objects that typically are made from natural terra cotta or clay such as trivets, garden ornaments, supports or feet for plant pots, dishes, spoon or utensil rests, etc.
Natural clay has been used for generations for horticultural pots such as flowerpots and other containers as well as for making other objects. While such products made from clay are aesthetically pleasing, they are susceptible to breaking when dropped and to cracking from exposure to freeze-thaw cycles in cold weather, particularly if they are wet or contain wet soil. Consequently, in colder climates ordinary clay pots must be brought indoors during the winter months and special care must be taken in handling such pots to avoid breakage. Furthermore, clay pots are susceptible to the permeation of water and the use of an impermeable container under such pots is required to avoid damage to wood floors, carpeting, etc. Similarly, clay has limited use in producing a container for cooling beverage bottles, such as wine bottles, because of its water permeability and susceptibility to cracking due to handling as well as to exposure to low temperatures.
U.S. Pat. No. 2,810,989 describes lightweight horticultural containers made of sand coated with from 0.5 to about 15 wt. % by weight of sand of a thermosettable or thermoplastic resin, e.g., phenol formaldehyde resin or polyvinyl chloride; the resin is set following formation of the container. The amount of sand used is limited to that necessary to coat the sand particles so that the container has a high degree of capillarity in order to provide free transfer of moisture and air. The patent teaches that dry silica sand containing less than 3% clay should be used and that the resulting containers will be about 50% lighter than a standard clay pot of the same dimensions. The use of synthetic rubbers produced in latex form, such as butadiene-styrene copolymers, is also disclosed. However, their use is also limited to low concentrations, i.e., just enough to coat the sand based on the use of a rubber latex. The patent suggests that there is no advantage to using more than 15 wt. % resin by weight of the sand in the mixture.
U.S. Pat. No. 2,848,842 discloses forming plant containers from pulp furnish and including additives that inhibit root formation in order to prevent penetration of roots through the container walls. In example 2 of the reference, approximately 5 wt. % neoprene (polychloroprene) is included in the composition in the form of neoprene latex; additionally, zinc oxide and di-beta-naphthyl-p-phenylene diamine are also included as xe2x80x9ccompounding ingredients for the neoprene rubber.xe2x80x9d The function of these additives is not disclosed, but it is believed that under appropriate conditions zinc oxide can function as a curative for neoprene and the p-phenylene diamine as an antioxidant or stabilizer. The patent states that plant containers were molded by xe2x80x9ca conventional pulp molding processxe2x80x9d, but neither general details of such a process nor the specific conditions used to mold the containers of the example are disclosed. A separate root inhibitor chemical (pentachlorophenol) was included in the composition.
U.S. Pat. No. 4,193,909 discloses a resin-aggregate mixture comprising polyurethane resin, aggregate (sand), silane compounds, iron oxide and powdered thermoplastic resins that are molded to form flowerpots and saucers, cured and subsequently are baked at a temperature sufficient to fuse the thermoplastic resin to provide a pot having air permeability but resistance to the permeation of water. The patent fails to disclose the use of several required elements of the present invention including vulcanizable elastomer, clay, and an odor masking agent. Furthermore, as a consequence of using different components in preparing the mixture of the reference, the containers molded therefrom are not disclosed as having the look and feel of clay, nor is there any indication of improved low temperature or mechanical stability.
U.S. Pat. No. 4,950,216 discloses the use of various materials to produce films or sheets that can be formed into overlapping folds so as to produce a flowerpot shape. Useful materials are said to include foil, cellophane, paper and processed organic polymer such as polypropylene and including crosslinked polymers, provided that the material is a film or sheet and is flexible. A flowerpot made from the folded sheet or film material is said to be up to 20.0 mils in thickness. Related patents U.S. Pat. Nos. 4,773,182 and 4,897,031 disclosed articles made from the sheet forming materials just described and to an apparatus for folding and forming such articles.
The general formulating and use of nitrile elastomers is described in a chapter of xe2x80x9cThe Vanderbilt Rubber Handbookxe2x80x9d, Thirteenth Edition, R. F. Ohm, Editor (1990). The chapter, written by J. R. Purdon, includes information on the use of carbon black and mineral fillers, vulcanization systems, blends, processing and properties.
It would be desirable to have improved molding compositions and molded articles made from such compositions that have the look of natural clay, are capable of being formulated so as to have the feel of natural clay, but are more resistant to breakage and cold temperatures than those fabricated from ordinary fired clay.
A composition prepared by forming a mixture comprising, on the basis of parts by weight per hundred of elastomer or rubber, phr: (a) 100 phr of at least one vulcanizable elastomer or a mixture of at least one vulcanizable elastomer with at least one thermoplastic polymer or thermoplastic elastomer; (b) from about 150 phr to about 500 phr of at least one mineral filler; (c) from about 0.1 phr to about 10 phr of at least one pigment or colorant; and (d) at least one vulcanizing agent in sufficient quantity to substantially fully vulcanize said at least one vulcanizable elastomer. Optionally the composition can include from about 0.01 to about up to about 10 phr of at least one odor masking agent. Preferably the following components are employed: the vulcanizable elastomer is a mixture of butadiene-acrylonitrile copolymers and styrene-butadiene copolymers, the mineral filler includes a significant amount of clay, the colorant includes red iron oxide and the odor masking agent, when used, is an extract of vanilla. The composition is usefully molded and vulcanized to form objects having the look of clay, are capable of being formulated so as to have the feel of natural clay, as well as having improved low temperature and mechanical stability. Useful objects molded from the composition include horticultural pots such as flower and planting pots, saucers used with such pots, beverage coolers such as wine bottle coolers and other items traditionally made from natural clay and terra cotta.